The conventional way to generate a second harmonic of light uses a slab of optically non-linear crystal that is illuminated by a laser beam. For example, a beam produced by a diode laser has a wavelength of 980 nm (infrared light). It can be converted into a beam with the wavelength of 490 nm (green light) by transmitting the former through an optically non-linear crystal. The process is used in, e.g., a green-light laser pointer.